Heating device and method for detecting failure of heating device

Abstract

A heating device (100) comprises: a heater (10) for heating an item (1); a temperature detection unit (20) for detecting the temperature of the item (1); and a temperature adjustment unit (30) for controlling the heater (10) on the basis of a target temperature and the detected value of the temperature detection unit (20) so that the temperature of the item (1) reaches the target temperature. The heating device (100) determines, as a system gain change rate, the rate of change from the initial value of a system gain determined as a ratio of a temperature increase value of the item (1) with respect to electric power inputted to the heater (10), and determines the rate of change in the heat retention of the item (1) using the system gain change rate.

The invention claimed is: 
     
       1. A heating device that includes a heater configured to heat an item, a temperature detection unit configured to detect a temperature of the item heated, and a temperature adjustment unit configured to control the heater on the basis of a detected value of the temperature detection unit and a target temperature so that the temperature of the item heated reaches the target temperature, the heating device comprising:
 a system gain change rate calculation unit configured to obtain a temperature increase value of the item heated from the detected value of the temperature detection unit, obtain a system gain, which is a ratio of the temperature increase value of the item heated with respect to electric power inputted to the heater, and obtain, as a system gain change rate, a rate of change from an initial value of the system gain; and 
 a heat retention change rate calculation unit configured to obtain a rate of change in heat retention of the item heated from the system gain change rate. 
 
     
     
       2. The heating device according to  claim 1 , further comprising:
 a heater resistance value change rate calculation unit configured to obtain a resistance value of the heater from a voltage and a current applied to the heater and obtain, as a heater resistance value change rate, a rate of change from an initial value of the resistance value, 
 wherein the heat retention change rate calculation unit obtains the rate of change in heat retention of the item heated from the system gain change rate and the heater resistance value change rate. 
 
     
     
       3. The heating device according to  claim 1 , further comprising:
 a heater voltage change rate calculation unit configured to obtain, as a heater voltage change rate, a rate of change from an initial value of a voltage applied to the heater, 
 wherein the heat retention change rate calculation unit obtains the rate of change in heat retention of the item heated from the system gain change rate and the heater voltage change rate. 
 
     
     
       4. The heating device according to  claim 2 , further comprising:
 a heater voltage change rate calculation unit configured to obtain, as a heater voltage change rate, a rate of change from an initial value of a voltage applied to the heater, 
 wherein the heat retention change rate calculation unit obtains the rate of change in heat retention of the item heated from the system gain change rate, the heater resistance value change rate, and the heater voltage change rate. 
 
     
     
       5. The heating device according to  claim 1 , further comprising:
 a heat retention failure detection unit configured to detect a failure in the heat retention by comparing the rate of change in heat retention with a threshold for the rate of change in heat retention. 
 
     
     
       6. The heating device according to  claim 2 , further comprising:
 a heater resistance value failure detection unit configured to detect a failure in the resistance value of the heater by comparing the heater resistance value change rate with a threshold value for the heater resistance change rate. 
 
     
     
       7. The heating device according to  claim 3 , further comprising:
 a heater voltage failure detection unit configured to detect a failure in the voltage applied to the heater by comparing the heater voltage change rate with a threshold value for the heater voltage change rate. 
 
     
     
       8. A failure detecting method of a heating device that includes a heater configured to heat an item, a temperature detection unit configured to detect a temperature of the item heated, and a temperature adjustment unit configured to control the heater on the basis of a detected value of the temperature detection unit and a target temperature so that the temperature of the item heated reaches the target temperature, the failure detecting method comprising:
 obtaining a temperature increase value of the item heated from the detected value of the temperature detection unit, obtaining a system gain, which is a ratio of the temperature increase value of the item heated with respect to electric power inputted to the heater, and obtaining, as a system gain change rate, a rate of change from an initial value of the system gain; and 
 obtaining a rate of change in heat retention of the item heated from the system gain change rate and detecting a failure in the heating device depending on whether or not the rate of change in heat retention exceeds a threshold value.